Tainted Promise
by Ailisu
Summary: An executive and a traitor. They parted ways, but he should have known. His heart had been tainted by him since a long time ago. " One day, you'll see. I'll be a great mafia, then I won't even need you as a partner, stupid Dazai! "
1. Stupid Dazai

**A/N:** I just caught up with the series yesterday, so if there's any mistakes, well, be nice? English isn't my main language either but I've drafted up the storyline for this fic. I hope you enjoy! :)

 _italics: words from the past_

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 **Chapter 1: Stupid Dazai**

 _"Because Chuuya is weak, I'll always be your partner."_

"What a dirty liar..."

The words escaped his lips in a mutter. He'd known him for close to a decade, yet there's only a few words that can describe him. Annoyance, traitor, dirty bandaged freak, suicidal maniac-

"Chuuya-san? "

The executive's eyes snapped open, his train of thoughts disturbed. Maybe its not a few words but rather, he had too much to say about Dazai. He blamed it on being his partner for years. That ungrateful bastard. A book was covering his face and he pulled it off by the spine before raising a brow at Higuchi.

"Um, you've been here for hours, do you need anything from the Black Lizards? "

Her eyes shifted to the plate of untouched cake and tea. The executive had surprised her, slamming the door open just hours ago and settling on the couch without a word. Maybe Chuuya just had a bad day. But she still needed to know why he was here as the superior of her group.

He ignored her, draping his dark inner coat over his shoulder as he stood.

"Foreign affairs are all taken care of so I'll be staying in Yokohama for a while."

Keeping him here in Yokohama, he wondered if the boss had planned something. Or maybe he's just worried about being an enemy of that person.

"The black lizard won't be needed for this war so I'll be handling all matters with the Armed Detective Company. "

Higuchi blinked, replying with a simple 'yes,sir'. But as the executive was about to leave, she continued to speak.

"Pardon me for saying this but you seem to really hate Dazai Osamu. "

Higuchi was only curious, afterall Akutagawa looked like he secretly respected him though there was also hatred for that man. She waited, the silence was deafening and she wondered if she'd mentioned a taboo topic. As Chuuya spoke, she swore she could almost hear a 'tsk' coming from the man.

"Of course, he betrayed us."

He betrayed **him**.

His brows furrowed, turning on the knob as he left for his mission. He won't let that suicidal maniac die so easily. At least not until he gave him a reason on why he abandoned him.

"Stupid Dazai..."

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 **A/N** : I'll update the next chapter next time, it'll get better. This story goes to the past and well, some developments. Reviews are very welcomed since its a new fic, I want to know what you guys think about it. :)


	2. Liar

**A/N:** This ch happens in the past, soukoku around the age of 14-16.

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 **Ch. 2 Liar**

"I wonder what we're going to do today. Practicing our ability? Killing? "

The light haired teen folded his hands behind his head. The hallways were dark and some bulky men in suit walked passed them with weapons in their hands. Chuuya didn't even bother to look at them, this was normal in the mafia. Instead, he glanced at the messy haired boy walking alongside him.

He's always been a weird kid, but as much as he hated to say it, he respected Dazai. Though he'd never say it, knowing they were compatible during training made him feel proud of his ability.

"Chuuya."

The young mafioso blinked, didn't expect to hear his name coming from him. Usually he'd call him 'shortie' or something as insulting.

"What? Stupid Dazai."

"Don't you think the mafia is boring?"

He snapped his head at the bandaged boy, the halls were empty but words like that could be dangerous here.

"What are you talking about? The boss favors you and we've been here for as long as I remember, what else can we do?"

"'Favors', hm? "

There was coldness in his words. Though there were many secrets kept from him between Dazai and the boss, he could tell something had happened again. Though he had a great ability, he was still a subordinate. But what he could see between the boss and his partner...it didn't seem like loyalty to Mori but more of 'shackles' for Dazai to stay under him.

Chuuya gave a light punch to his shoulder, grinning.

"You'll become a useless, suicidal man in the future if you keep thinking of stupid things. Then it'll be too easy for me to surpass you and become an executive. "

Dazai blinked, muttering under his breath.

"At least then I'll still be taller than you. "

Chuuya stopped on his track. Here he was trying to lift his spirits up.

Unbelievable.

"Wha-just you wait, stupid Dazai! I'll definitely be taller than you. You know, I drink milk everyday! "

The nullifier paused, but as he turned to face the other, he threw Chuuya a smug look. Slipping a hand in his pocket, he poked a finger on his forehead. Chuuya blinked.

"Heh. Does playing with your lame gravity finally mushed your brain? You won't surpass me with just milk. I bet I'll be an executive before you, shorty. "

Chuuya fumed, anger rising up to the point that his cheeks turned red infront of the boy who was smiling innocently. Disgusting. Stupid Dazai.

"I'll kill you!"

The light haired teen threw a punch but as always, Dazai stepped to the side, catching him by the wrist so he couldn't use his ability. Chuuya let a small growl, hissing at him.

"One day, you'll see. I'll be a great mafia then I won't even need you as a partner. "

Dazai blinked, looking at the light haired teen who looked so pissed, tears were probably going to form if he kept teasing him.

How amusing.

"What are you talking about?"

Chuuya's light blue eyes widened at the sight. Dazai was laughing and even with the bandage over him eye and the dirt on his coat, a smile spread over his lips. He almost couldn't pull away from the hold that Dazai had on his wrist. The brown haired mafioso grinned.

How can the mafia be so boring with a partner like Chuuya?

 _"Because Chuuya is weak, I'll always be your partner. "_

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 **A/N:** I decided to update a little early since I had positive feedback from tumblr. Feel free to follow me ailisu or the link from my profile.

Reviews, fav and alerts are much appreciated cause its a new idea. Thank u! : )


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